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Processing of mixtures
If Masterbatch or Recyklat are added to a base polymer the rheological and thermal characteristics of the mixing change according to the composition ratio. In order to determine the pressure throughput behavior of such mixings in single screw extruders, the corresponding material parameters of each single polymer mixing have to be determined again. This procedure is very cost- and time consuming.
REX/PSI implements an approach for determining the throughput or melting behaviour of a polymer mixture, for example, by knowing the individual material properties and the mixing ratio. In order to define a mixture, both materials (polymer-polymer or polymer-filler) must first be selected (see input of mixtures). It is also essential to specify the mixing ratio. Optionally, the rheological parameters of the mixture can be specified (viscosity→calculation function→rheological data) if these are known from measurements. Alternatively, an approximate calculation of the viscosity of the mixture from the viscosities of the individual materials is also possible, whereby several mixing rules are implemented (see input of mixtures). The tribological data of the mixture can also be specified. These can either be calculated using the selected mixing rule (only if both material data sets contain tribological data) or entered manually. However, the determination using the mixing rule does not accurately reflect the real data.
The rheological as well as the thermodynamic characteristic data of binary system materials (e.g. solid and melt enthalpies of polymer mixings) cannot be determined sufficiently via a linear averaging of the data of the base components. All material data for the polymer mixing has to be determined for the simulated processes. This requires a lot of measurements even before the actual simulation procedure. The material data of mixings will be determined from the material data of the single components by calculations with REX/PSI, if only these material data of the single components is available.
The calculation in REX/PSI is carried out as usual, but with the defined averaged material data of the individual components.